1. Field of the Invention
The present invention relates to an inkjet recording head, and more particularly relates to a circuit provided in the recording head, the circuit being configured to confirm the state of a connection between the recording head and the main body of a recording apparatus.
2. Description of the Related Art
A method of using an electromechanical transducer such as a piezo element and a method of ejecting droplets by using thermal energy are known as typical liquid (ink) ejecting methods that are used for an inkjet recording head mounted on an inkjet recording apparatus. Of the above-described methods, inkjet recording heads configured to heat liquid through an electrothermal conversion element (heater) and eject droplets through the effect of film boiling have become widely available.
A recording apparatus provided with the inkjet recording head can output high-quality text data or image data at a low cost. A unit configured to electrically connect the recording head to the main body of the recording apparatus is provided on the recording head and a carriage on which the recording head is mounted so that the recording head is reciprocated. More specifically, a plurality of contact points is provided on the carriage. When the recording head is mounted on the carriage, the contact points are brought into contact with a plurality of electrical contact points provided on the recording-head side so that an electrical connection is established between the recording head and the main body of the inkjet recording apparatus.
A recording head and a recording apparatus that are provided with a configuration used to monitor the electrical connection state have been known. For example, a record signal, a clock signal used to transfer the record signal, and so forth are transmitted from the main body of the recording apparatus to the input end of the recording head. There are an AND circuit configured to calculate a logical product of control signals used for recording operations performed through the record signal, a recording head provided with an output end used to externally transmit data of the calculation result, and so forth. Thus, the configuration used to monitor the electrical connection state of the recording head is provided on the recording head. Consequently, a disorder on an image such as the missing of record dots, a malfunction in the recording head, the malfunction occurring due to insufficient connections of the contact points, and so forth were reduced. The confirmation and/or monitoring the state of an electrical connection between the head and the recording apparatus was important for a head cartridge that is integrated into an ink tank and that is mounted on the main body of the inkjet recording apparatus in a removable manner. When a malfunction occurred in the head of the head cartridge, it was difficult to use ink contained in the ink tank provided in the head and the ink was wasted.
As described above, the inkjet recording head has been used based on the premise that the inkjet recording head is mounted and/or removed on and/or from the recording apparatus by a user, so as to be replaced with another. When a head cartridge integrated into an ink tank is used, a new inkjet recording head is mounted on the recording apparatus each time ink is consumed. Since the recording head is mounted and/or removed on and/or from the recording apparatus by the user, a system that can confirm the state of the electrical connection between the main body of the recording apparatus and the recording head each time the recording head is mounted and/or removed on and/or from the recording apparatus is preferred. As for the mounting and the removing the recording head, determining whether the recording head is mounted at a predetermined position with stability is preferred. It is important to reduce malfunctions in the recording head, the malfunctions occurring due to an insufficient connection between the recording head and the main body of the recording apparatus, by determining an end with insufficient connection and/or detecting shorting of one end and the other end, for example.
For example, if the recording head is mounted on the recording apparatus while a dust or the like is attached to a part of the electric contact unit of the recording head, the connection may be insufficient only for some ends to which the dust is attached.
According to U.S. Pat. No. 5,828,386, a logical product is calculated for each of signal system input ends used to transmit signals to a recording head. If the level of the output is lower than or equal to a predetermined voltage level, it is determined that a connection between the recording head and an apparatus is insufficient and a warning is issued. In that case, if any single end with insufficient connection is detected, it is determined that there is a malfunction in the recording head itself. Therefore, it has been difficult to detect whether the recording head is mounted on a predetermined position, whether the connection of each end is insufficient, or whether the connections of only some of the ends are insufficient on the recording-apparatus side.
According to U.S. Pat. No. 7,467,864, a circuit configured to output data of the state of a connection between a recording head and a recording apparatus is provided. A latch signal and/or a heater-drive signal transmitted to the recording head is inversed before being transmitted to the circuit so that a noise transmitted from the circuit during data recording does not become a noise affecting recorded data. However, the circuit disclosed in U.S. Pat. No. 7,467,864 is configured to collectively determine whether signals transmitted to the recording head are constant signals instead of separately determining the connection state of a predetermined end.